I've got a similar mower. (42" Craftsman LT 1000) And have the same issues. I bought new mulching blades (IIRC they were called Gator blades) and that helped out a lot, but it will still clump with the heavy spring grass. I think the main problem is the mower deck isn't designed for mulching, it is set up for side discharge and the "mulching plate" is simply a block off for the discharge. The bottom of a deck with a "proper" mulching kit will have baffles to keep the clippings recycling rather than being passed to the other blades for discharge. I find that the time savings of the lawn tractor outweighs the mediocre cut quality. I also have a Lawn Boy (last of the two strokes) walk behind that does an excellent job but it takes well over an hour and a half for me to cut the lawn. I'd give the Gator blades a try, they were about 40 bucks a pair.

The best source of information about Corn Gluten Meal would probably be the Iowa state University researchers that discovered its use. They do indicate that CGM will suppress the growth of some grass seedlings. I am not able to find anything to indicate it will stop the growth of grass from roots. Here is a link that might be useful: Corn Gluten Meal

Just to give another perspective . . . my husband, the one who mows the lawns in our family, doesn't like this kind of edge because he can't mow up to the edge since the wheels of the lawn mower fall into the ditch, and neither of us wants to weed whack the edge. I like a well done cut edge, but I'm not about to start mowing the lawn, so we reached a compromise. I used commercial grade black plastic edging, tucked down deep enough so that it is hidden behind the grass and lined on the inside edge of the garden bed with a single course of brick. It allows him to run the wheels of the lawn mower on the brick and gives me a bit of a masonry edge to slow down any crawlers trying to get into the garden from the "lawn" like clover or various weeds. It looks tidy, though not perhaps as nice as the trench style, and is a compromise we can both live with. We have not had problems with the edging lifting in three years (but we don't have much clay in our soil.) It does require paving brick, not wall brick which will crumble when it freezes.

Hello Rod, I had the same problem, tried several different chemicals, none with success. Either they didn't kill the Kikuyu, or killed part of my lawn. However, eventually I did find a way. Firstly I bought Freezone Tuffweed, which contains a higher concentration of glyphosate than Roundup, which costs less and you only need a smaller quantity. I purchased a Weeding Brush, several different makes available, filled it with Tuffweed, and went onto the lawn, choosing an area to treat, and began stroking the brush along every Kikuyu runner I could see. As you push on the brush, it allows chemical to flow to the brush head, so you can target where your chemical is going far better than spraying, and you can do it even on a windy day! Once you have done it a few times, you can become quite good, and application gets more precise, so damage to your lawn or other plants becomes negligible. This kills the whole plant as it's systemic, from runner to root. It's the only way I know of killing Kikuyu permanently. Hope this is of benefit Rod.